T cell-mediated immune responses are important in the control of Herpes simplex virus (HSV) infections. However, little is understood about the characteristics of the T cells which are active, about the control of these cells and about the variety of antigens which are recognized in these responses. In this study we wish to build on our experience with human T cell responses to HSV and to examine several new problems in this area using two functional in vitro assays of cellular responses to HSV. First, the possibility of suppressor cell regulation of T cell proliferative responses, as suggested from other studies, will be tested in syngeneic cell mixing studies of donor peripheral blood mononuclear cells (PBMC) obtained at different phases of disease and by mixing PBMC with HSV-specific T cell lines. If identified, the suppressor cells will be characterized with these methods. Second, the role of virus early antigen recognition, which is known in other DNA virus systems, will be studied in human anti-HSV proliferative responses using novel cultures which inhibit late polypeptide synthesis i.e., non-permissive monocytes and XC cells, Ts mutants and antibiotics which specifically inhibit viral DNA synthesis and late polypeptide production. Third, cytolytic T cells (Tk), which are known to be important in the control of some viral infections, and are controlled by suppression in animal models of HSV will be studied. Conditions will be explored for the reproducible production of Tk with special attention to the antigenic stimulus, eg., killed virus versus infected living cells, to the role of suppression, and to the role of growth and differentiation factors. Fourth, genetic restriction of the Tk will be studied with HLA-typed target cells from the Georgetown Cell Bank. In addition, fine antigen specificity of the Tk cells will be studied with a panel of genetically distinct HSV-1 and HSV-2 isolates as well as with target cells hosting permissive and non-permissive infections, to reveal the role of type-specific reactions and the contribution of viral early antigens in Tk reactions. These studies will contribute to understanding HSV immunobiology and may suggest novel approaches for treatment of severe disease and will develop methods useful to monitor immune responses to HSV in the development of protective vaccines.